Rheostat with fixed resistors



06L 1953 w. w. LITTLETON RHEOSTAT WITH FIXED RESISTORS 3 Sheets-Sheet 1Filed April 22, 1955 ATTORNEY lOc 0 r.28,1958 -w. w. LITTLETQN ,85 7

RHEOSTAT WITH FIXED RESISTORS Filed April 22, 1955 3 Sheets-Sheet 3Fig.7

BM 34 W IN VEN TOR. WILLIS W. LITTLETON ATTORNEY tent 2,858,397 PatentedOct. 28, 1958 RHEOSTAT wrrrr rixnn nnsrsrons Willis W. Littleton, Boone,N. (1., assignor to international Resistance Company, Philadelphia, Pa.

Application April 22, 1955, Serial No. 563,254

14 Claims. (Cl. 201-55) This invention relates to a rheostat, i. e., avariable resistor, such as a volume or tone control associated in aconvenient manner with one or more fixed resistors as a single unit.

In many electronic circuits used in electronic apparatus, such as radioand television equipment, it is necessary to provide a variable resistorhaving in series therewith, one or more fixed resistors. Heretofore,this was accomplished by wiring the various separate fixed and variableresistor components together in the desired arrangement. However, thismethod has many disadvantages in the manufacture of such apparatus. Thewiring of such units must be done by hand and is time consuming andexpensive, in addition, it is space consuming.

There are available, variable resistors having a stop for limitingtravel of the movable contact along the resistance path so that aportion of the path forms a fixed resistor in series with the variableresistors. However, such a unit provides only one fixed resistor andalso shortens the length of the variable resistor path therebydecreasing the resistance value obtainable.

It is therefore an object of this invention to provide a variableresistor with one or more fixed resistors in a single compact unit.Another object is to provide a variable resistor with one or more fixedresistors in the single unit without shortening the resistance path ofthe variable resistor. A further object is to provide a combinedvariable resistor and fixed resistor unit which will economize themanufacture of electronic apparatus, such as radio and televisionequipment. Other objects of the invention will in part be obvious andwill in part appear hereinafter.

The invention accordingly comprises the features of construction,combinations of elements, and arrangement of parts, which will beexemplified in the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

Fora fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

Figure l is a perspective view of the unit;

Figure 2 is a sectional view of the unit;

Figure 3 is an end view of the unit without the cover looking from leftto right in Figure 2;

Figure 4 is a plan 'view of the fixed resistor element;

Figure 5 is a plan view of the variable resistor element;

Figure 6 is a semi-diagrammatic arrangement of the variable resistor andfixed resistors;

Figure7 is a circuit diagram of the resistor arrangement shown in Figure6;

Figure 8 is a modified semi-diagrammatic arrangement of, the variableand fixed resistors;

Figure 9 is a circuit diagram of the resistor arrangement shown inFigure 8;

Figure 10 shows a further modified arrangement of the variable and fixedresistors; and

arrangement of the strips.

Figure 11 is a circuit diagram of the resistor arrangement shown inFigure 10. 7

Referring to Figure 2 of the drawing, the unit in general comprises abase plate 111 of an electrical insulating material. A fixed resistorelement 11 coated with one or more resistance strips is mounted on oneface of the base plate 1%. A variable resistor element 12 coated with asingle resistance strip is mounted on the fixed resistor element 11 withthe resistance strips on the two elements being insulated from eachother. The ends of the strips on the fixed resistor element 11 areconnected to the strip on the variable resistor element 12 and ifdesired, to each other to form the desired series or parallel A shaftgenerally indicated at 13 is rotatably supported on the base plate 10 tocarry a contact which slidably engages the strip on the variableresistor element 12. Thus, a variable resistor is connected as desiredwith fixed resistors in a circuit arrangement.

Referring to Figures 1, 2 and 3, the unit in detail comprises an annularbase plate 10 molded from a plastic having good insulation properties.The base plate 10 has a central aperture 10a and four ribs ltlbextending radially from and spaced around its periphery. Each of theribs 10b has a hole therethrough. The fixed resistor element 11comprises a C-shaped sheet 15 (Figure 4) of an insulating materialhaving four tabs 15a, 15b, 15c and 15d extending radially from andspaced around its periphery. These tabs are circumferentially spaced thesame distance as ribs 19b on base plate 10 with two of the tabs 15a and15d being adjacent the free ends of sheet 15. Each of the tabs has ahole 152 therethrough. The sheet 15 is coated with one or moreresistance strips in a manner to be explained later to complete thefixed resistor element 11 which is mounted on base plate 10 aroundaperture ltia, the tabs overlying the ribs 10b and the resistance stripsfacing away from the base plate 10.

The variable resistor element 12 comprises a C-shaped sheet 16 (Figure5) similar to fixed resistor sheet 15 but having only two radiallyextending tabs 16a and 16b adjacent its free ends. Tabs 15a and 16b arecircumferentiallythe same as tabs 15a and 15d to be superimposed thereonand each has a hole 16c therethrough. Sheet 16 is coated with aresistance material in a manner to be explained later to complete thevariable resistor element 12. This variable resistor element 12 issuperimposed on the fixed resistor element 11 with tabs 16a and 16boverlying tabs 15a and 15d respectively and with the variable resistorstrip facing away from the base plate 10. A U-shaped metal clip 17a fitsover the end of the rib 10b opposite tabs 15a and 16a, one leg of theclip fitting be tween tab 15a and tab 16a. A second U-shaped clip 17bfits over the rib 10b engaged by tab 15a in the same manner with a legbeing similarly located between tabs 15d and 16b. Each of the clips 17aand 17b has holes in its legs in alignment with the holes in the ribsand tabs. A headed metal rivet 18 fits through each set of aligned holeswith the head 13a engaging the resistance strip on 'the variableresistor element 12. A metal terminal 19 fits on the other end of eachrivet 18 and against clips 17a and 1752. An annular flange 13b on theother end of the rivets sandwiches the tabs, ribs, clips and terminalstightly together. Thus, the resistance strip on the variable resistorelement 12 is connected to the resistance strips on the fixed resistorelement 11 through the rivets 18 and U-shaped clips 17. Additionalheaded rivets 20 extend through the holes of tabs 15b and 150 alignedwith holes 100 in ribs 101) with the heads 20a engaging the resistancestrips on the fixed resistor element 12. Metal terminals 21 fit on theother ends of the rivets 20 which are then formed with annular flanges20b to sandwich the tabs, ribs and terminals together.

A shaft 13 having a reduced end portion 13a extends through aperturelilo in base plate ltl with the reduced end portion 22a extending beyondthe face of base plate which has the resistor elements attached thereto.A cylindrical metal bushing '23 having a mounting plate secured to oneend thereof fits around shaft 13 so that the mounting plate engages theface of base plate ltd opposite the resistor elements. A snap ringfitting in an annular groove 13b in the shaft 13 engages the end of thebushing 23 to hold the bushing against the base plate lit). A contactcarrier plate 26 of insulating material is mounted on reduced endportion (Figure 2) of the shaft and a metal contact member (Figure 3) issecured to the carrier plate 26 by lugs 27a extending through holes 26:;in the carrier plate 26. Contact member 27 has a pair of contact arms27!) (Figure 2) slidably engaging the resistance strip on the variableresistor element 12 and a spring arm 27c slidably engaging a metalcollector ring 28 which is mounted on the base plate 10 (Figure 2);collector ring 28 is connected to terminal 29. A drive plate 359 (Figure2) is also mounted on reduced end portion 13a and abuts against thecarrier plate 26. The end of the shaft 13 is flanged at 130 to form aforce fit with drive plate 30. Drive plate 30 has a drive flange 30afitting into a slot 26b in the carrier plate 26 and a stop flange Sill)(Figure 3). A cup shaped cover 31 fits around the reduced end portion13a of the shaft and the elements mounted thereon and abuts against thebase plate lb. The cover 31 has tabs 31a (Figure 1) extending over theedge of base plate 10 and bent into engagement with the face of thebushing mounting plate 2% to hold both the cover and the bushing 23 tothe base plate 149. The cover 31 also has an indentation 31b (Figure 2)extending into the path of rotation of the stop flange 30b of the driveplate 3!? to limit rotation of shaft 13 so contact arms 27b will notmove from the ends of variable resistor element 12.

Figures 6, 8, and 10 show various arrangements of the resistance stripson the fixed resistor element l1 and the variable resistor element 12.In the arrangement shown in Figure 6, the sheet 15' of fixed resistorelement 11 is coated with a resistance strip which extends between tabs15a and 15b to form one resistor 32. Another resistance strip extendsbetween tabs 15c and 15d to form a second resistor 33 insulated from thefirst resistor 32. The sheet 16 of the variable resistor element l ft iscoated with a resistance material extending between tabs 16a and 16b toform a variable resistor 34-. One end 16a of variable resistor 34 isconnected to end 15a of fixed resistor 32 through a rivet l8 andU-shaped clip 17a (Figure 2) as previously described and asdiagrammatically indicated by dotted line 35. The other end 16b of thevariable resistor 34 is similarly connected to end 15:! of fixedresistor 33 as diagrammatically indicated by dotted line 36. Thus, asshown in Figure 7, the variable resistor 34 has a fixed resistor 32connected in series with one end and a fixed resistor 33 connected inseries with its other end.

In the arrangement shown in Figure 8, the sheet 15 of fixed resistorelement 11 is coated with a resistance strip extending between tabs 15aand 15b to form a fixed resistor 32a and with a strip extending from tab151; to tab 15c to form a second resistor 3'7 connected at one end toresistor 32a. The variable resistor element 12 is the same as previouslydescribed. In this arrangement one end 16a of variable resistor 34- isconnected to one end 15a of fixed resistor 320 as indicated by dottedline 35a. As shown in Figure 9, this arrangement forms the variableresistor 34 with the fixed resistors 32:; and 37 connected in serieswith one end thereof.

In the arrangement shown in Figure 10, the resistor elements lit and 12are the same as shown in Figure 6. However, in this arrangement, one end15a of fixed resistor 32 is connected to one end 16!: of variableresistor 34 as again indicated diagrammatically by dotted line 35; end15a is also connected to one end 15d of fixed resistor 33 asdiagrammatically indicated by dotted line 37. This arrangement, as shownin Figure 11, provides the variable resistor 34 having in seriestherewith the parallel fixed resistors 32 and 33,.

Other arrangements can be obtained by connecting the fixed resistors toeach other and to the variable resistor to obtain a variety or" desiredcircuit arrangements. Sheet 15 may have more than two resistors byproviding additional tabs on the sheet with resistance coatingstherebetween which will be obvious from the above description. Thus,there is provided a single unit containing a variable resistor connectedin any desired circuit arrangement with one or more fixed resistors.Furthermore, the construction of the unit provides for ease ofmanufacture of any desired circuit arrangement from the same combinationof elements. For any change in the circuit arrangement it is onlynecessary to provide a fixed resistor element having the desired numberand arrangement of fixed resistors while the remaining elements remainthe same for each arrangement.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. A resistor comprising the combination of a thin sheet of insulatingmaterial, a resistance material strip on said sheet, a second sheet ofinsulating material overlying said first sheet, a resistance materialstrip on said second sheet but insulated from the strip on said firstsheet, a connection between one end of the strip on said first sheet andone end of the strip on said second strip and a contact movable alongthe strip on said second sheet.

2. A resistor comprising the combination of a thin sheet of insulatingmaterial, a plurality of resistance material strips on said sheet, asecond sheet of insulating material overlying said first sheet, aresistance material strip on said second sheet but inulated from thestrips on said first sheet, a connection between an end of the strip onsaid second sheet but insulated from the strips on said first sheet, anda contact movable along the strip on said second sheet.

3. A resistor comprising the combination of a sheet of insulatingmaterial, two resistance material strips on said sheet in spacedrelation, a second sheet of insulating material overlying said firstsheet, a resistance material strip on said second sheet but insulatedfrom the strips on said first sheet, a connection between one end of thestrip on said second sheet and one of the strips on said first sheet, aconnection between the other end of the strip on said second sheet andthe other of the strips on said first sheet, and a contact movable alongthe strip on said second sheet.

4. A resistor comprising the combination of a sheet of insulatingmaterial, two resistance material strips on said sheet, a second sheetof insulating material overlying said first sheet, a resistance materialstrip on said second sheet but insulated from the resistance strips onsaid first sheet, a connection between one end of the strips on saidfirst sheet and one end of the strip on said second sheet, a connectionbetween the other end of the one strip on said first sheet and the otherstrip on said first sheet and a contact movable along the strip on saidsecond sheet.

5. A resistor comprising the combination of a sheet of insulatingmaterial, two resistance material stripsonsaid sheet in spaced relation,a second sheet of insulating material, a resistance material strip onsaid second sheet but insulated from the strips on said first sheet, aconnection between one end of the strips on said first sheet and one endof the strip of said second sheet, a connection between said one end ofsaid one strip and the other strip on said first sheet and a contactmovable along the strip on said second sheet.

6. A resistor comprising the combination of a plate of insulatingmaterial having a hole therethrough, an annular thin sheet of insulatingmaterial mounted on a face of said plate and around said hole, aplurality of resistance material strips on said sheet, a second annularthin sheet of insulating material mounted on said plate and overlyingsaid first sheet, a resistance material strip on said second sheet butinsulated from the strips on said first sheet, means connecting an endof the strip on said second sheet to at least one of said strips on saidfirst sheet, a rotatable shaft extending through the hole in said plateand a contact mounted on said shaft and slidably engaging the strip onsaid second sheet.

7. The combination as set forth in claim 6 in which the means forconnecting the resistance material strips comprises a U-shaped metalclip fitting over the edge of the plate with one leg thereof contactinga strip on said first sheet and the other leg engaging the other face ofsaid plate and a metal rivet extending through the sheets, plate andboth legs of the clip and at one end engaging the strip on said secondsheet and at the other end engaging the clip.

8. A resistor comprising the combination of a plate of insulatingmaterial having a hole therethrough, a thin annular sheet in insulatingmaterial mounted ona face of said plate and around said hole, tworesistance material strips on said sheet in spaced relation, a pair ofU-shaped metal clips fitting over the edge of the plate so that the legsof said clips straddle said plate, one of said clips having a legcontacting one of said strips and the other clip having a leg contactingthe other of said strips, a second thin annular sheet mounted on saidplate and overlying said first sheet, a resistance material strip onsaid second sheet having one end overlying the legs of one clip and theother end overlying the legs of said other clip, metal rivets extendingthrough each end of the strip on said second sheet the strips on saidfirst sheet, the legs of the clip and the plate, each rivet having oneend engaging the strip on said second sheet and the other end engagingthe clip, a rotatable shaft extending through the hole in said plate anda contact mounted on said shaft and slidably engaging the strip on saidsecond sheet.

9. A resistor comprising the combination of a plate of insulatingmaterial having a hole therethrough, a thin annular sheet of insulatingmaterial mounted on a face of said plate and around said hole, a firstresistance material strip on said sheet, a second resistance materialstrip on said sheet having an end engaging one end of said first strip,a U-shaped metal clip fitting over the edge of said plate so that thelegs thereof straddle said plate, one leg of said clip engaging theother end of said first strip, a second thin annular sheet of resistancematerial mounted on said plate and overlying said first sheet, aresistance material strip on said second sheet having one end overlyingthe legs of said clip, aligned holes in the one end of the strip on saidsecond sheet, the other end of said first strip, the legs of said clipand said plate, a metal rivet extending through the aligned holes havingone end thereof engaging the strip on said second sheet and the otherend engaging the clip, a rotatable shaft extending through said firstmentioned hole in said plate and a contact mounted on said shaft andslidably contacting the strip on said second sheet.

10. A resistor comprising the combination of a plate of insulatingmaterial having a hole therethrough, a thin annular sheet of insulatingmaterial mounted on a face of said plate and around said hole, a firstresistance material strip on said sheet, a second resistance materialstrip on said sheet having an end connected to one end of said firststrip, a U-shaped metal clip fitting over the edge of said plate withthe legs thereof straddling said plate, one of the legs of said clipengaging said one end of the first strip, a second thin annular sheet ofinsulating material strip on said second sheet having one end overlyingsaid one end of the first mentioned strip, aligned holes through the oneend of the strip on said second sheet, the one end of said firstmentioned strip, the legs of the clip and the plate, a metal rivetextending through said aligned holes having one end engaging the stripon said second sheet and the other end engaging the clip, a rotatableshaft extending through said first mentioned hole in said plate, and acontact mounted on said shaft and slidably contacting the strip on saidsecon sheet.

11. A resistor comprising the combination of a plate of insulatingmaterial having a central aperture and a rib extending substantiallyradially from the periphery thereof, a thin annular sheet of insulatingmaterial mounted on a face of said plate and around said aperture, saidsheet having a pair of substantially radially extending tabs spacedaround the periphery thereof, one of said tabs overlying said rib, aresistance material strip on said sheet and extending along and betweensaid tabs, a U- shaped metal clip fitting over the edge of said rib withthe legs thereof straddling said rib, one of the legs of said clipengaging the portion of the resistance strip on the tab overlying saidrib, a second thin annular sheet I of insulating material mounted onsaid plate and overlying said first sheet, a tab on said second sheetoverlying the rib, a resistance material strip on said second sheethaving one end extending along the tab thereof, aligned holes throughthe overlying tabs, rib and legs of said clip, a metal rivet extendingthrough said hole having one end contacting the strip on the tab of saidsecond sheet and the other end contacting the clip, a rotatable shaftextending through said aperture and a contact mounted on said shaft andslidably contacting the strip on said second sheet.

12. A resistor comprising the combination of a plate of insulatingmaterial having a central aperture and a pair of substantially radiallyextending ribs spaced around the periphery thereof, a thin annular sheetof insulating material mounted on a face of said plate and around saidaperture, said sheet having four substantially radially extending tabsspaced around the periphery thereof, a first resistance material stripon said sheet extending along and between two of said tabs forming afixed resistor, a second resistance material strip on said sheetextending along and between the other two tabs forming another fixedresistor, one tab of each strip overlying a rib, a U-shaped metal clipfitting over the end of'each of said ribs, each of said clips having itslegs straddling its respective rib and one leg contacting the strip onthe respective tab, a second annular sheet of insulating materialmounted on said plate and overlying said first sheet, a pair of spacedtabs on said second sheet each overlying one of said ribs, a resistancematerial strip on said second sheet extending along and between the tabsthereof to form a variableresistor, aligned holes through said overlyingtabs, ribs, and legs of said clips, a metal rivet extending through eachset of aligned holes having one end contacting the variable resistorstrip and the other end contacting the clip, a rotatable shaft extendingthrough said aperture, and a contact mounted on said shaft and slidablyengaging the variable resistor strip.

13. A resistor comprising the combination of a plate of insulatingmaterial having a central aperture and a rib extending substantiallyradially from the periphery thereof, a thin annular sheet of insulatingmaterial mounted on a face of said plate and around said aperture, saidsheet having three substantially radially extending tabs spaced aroundthe periphery thereof, one of said tabs overlying said rib, a firstresistance material strip on said sheet extending along and between saidone tab and an adjacent tab to form a fixed resistor, a secondresistance material strip on said sheet extending along and between thethird tab and said adjacent tab to form a second fixed resistor having acommon tab with said first resistor, a U-shaped metal clip fitting overthe end of said rib with the legs thereof straddling said rib, one legof said clip contacting the strip on said one tab, a second thin annularsheet of insulating material mounted on said plate and overlying saidfirst sheet, a tab extending from the periphery of said second sheet andoverlying said rib, a resistance material strip on said second sheethaving one end extending along the tab thereof to form a variableresistor, aligned holes through said overlying tabs, rib and legs ofsaid clip, a metal rivet extending through said aligned holes having oneend contacting the strip on said second sheet and the other endcontacting said clip, a rotatable shaft extending through said aperture,a contact mounted on said shaft and slidably engaging said variable"resistor strip.

14. A resistor comprising the combination of a plate of insulatingmaterial having a central aperture and a rib extending substantiallyradially from the periphery thereof, a thin annular sheet of insulatingmaterial mounted on a face of said plate and around said aperture, apair of substantially radially extending tabs spaced around theperiphery of said sheet, one of said tabs overlying said rib, aresistance material strip on said sheet extending along and between saidtabs to form a first fixed resistor, a second resistance material stripon said sheet forming a second fixed resistor, means connecting one endof said second strip to the strip on said one tab, a -U-shaped metalclip fitting over the end of said rib with the legs thereof straddlingsaid rib, one of said legs contacting the strip on said one tab, asecond thin annular sheet of insulating material mounted on said plateand overlying said first sheet, a tab on said second sheet overlyingsaid rib, a resistance material strip on said second sheet having oneend I tending along the tab thereof to form a variable resistor, alignedholes through said overlying tabs, rib and legs of said clip, a metalrivet extending through said holes having one end contacting thevariable resistor strip and the other end contacting said clip, arotatable shaft extending through said aperture, and a contact mountedon said shaft and slidably engaging said variable resistance strip.

References Cited in the file of this patent UNITED STATES PATENTS BeckNov. 23,

